using UnityEngine;

namespace Unheimlich.World.HouseOfLeaves
{
    /// <summary>
    /// Animates the sand terrain shader progression based on the player's
    /// advancement through the corridor.
    ///
    /// Drives the _Progression float on the sand material from 0 to 1,
    /// simulating sand flooding the corridor as the player advances.
    /// </summary>
    public class SandTerrainController : MonoBehaviour
    {
        // ─────────────────────────────────────────────────────────────────────────
        // Serialized Fields
        // ─────────────────────────────────────────────────────────────────────────

        [Header("References")]
        [Tooltip("The HouseOfLeavesController driving the progression value.")]
        [SerializeField] private HouseOfLeavesController _controller;

        [Tooltip("The sand terrain Transform holding the sand material.")]
        [SerializeField] private Transform _sandTerrain;

        [Header("Progression Settings")]
        [Tooltip("Animation curve mapping progression [0,1] to shader value [0,1]. " +
                 "Use this to delay or ease the sand appearance.")]
        [SerializeField] private AnimationCurve _riseCurve = AnimationCurve.EaseInOut(0f, 0f, 1f, 1f);

        // ─────────────────────────────────────────────────────────────────────────
        // Private Fields
        // ─────────────────────────────────────────────────────────────────────────

        private Renderer _renderer;

        private static readonly int ProgressionID = Shader.PropertyToID("_Progression");

        // ─────────────────────────────────────────────────────────────────────────
        // Unity Messages
        // ─────────────────────────────────────────────────────────────────────────

        private void Start()
        {
            if (_controller == null)
            {
                Debug.LogError("[SandTerrainController] HouseOfLeavesController reference is missing.");
                return;
            }

            if (_sandTerrain == null)
            {
                Debug.LogError("[SandTerrainController] Sand terrain Transform is missing.");
                return;
            }

            _renderer = _sandTerrain.GetComponent<Renderer>();

            if (_renderer == null)
            {
                Debug.LogError("[SandTerrainController] No Renderer found on sand terrain.");
                return;
            }

            // Initialize shader progression to zero.
            _renderer.material.SetFloat(ProgressionID, 0f);
        }

        private void Update()
        {
            if (_controller == null || _renderer == null) return;

            float t = _riseCurve.Evaluate(_controller.Progression);
            _renderer.material.SetFloat(ProgressionID, t);
        }
    }
}